A well may be utilized to produce one or more reservoir fluids, such as liquid and/or gaseous hydrocarbons, from a subterranean formation. The well may include a wellbore, which extends between a surface region and the subterranean formation, and a production casing that extends within the wellbore and defines a casing conduit.
During construction and/or operation of the well, it may be desirable to stimulate and/or fracture the subterranean formation, such as to increase a flow, or production, rate of reservoir fluids therefrom. In general, this stimulating includes providing a stimulating fluid to the casing conduit, with the stimulating fluid flowing from the casing conduit into the subterranean formation to thereby stimulate the subterranean formation. Illustrative examples of stimulation processes include fracturing the formation and acidizing, or acid treating, the formation. Typically, this stimulating process may be repeated a plurality of times along a length of the production casing to stimulate a plurality of zones of the subterranean formation.
A number of processes have been utilized to stimulate subterranean formations. While these processes may be effective under certain conditions, they may be ineffective under others. As an illustrative, non-exclusive example, a well may include a wellbore with a long horizontal section. This long horizontal section may extend within the subterranean formation, and it may be desirable to stimulate a plurality of zones of the subterranean formation that may be distributed along the length of the horizontal section.
Traditional stimulating processes may include establishing fluid communication between the casing conduit and a given zone of the subterranean formation, providing the stimulating fluid to the given zone of the subterranean formation to stimulate the given zone of the subterranean formation, and then fluidly isolating at least a portion of the casing conduit from the subterranean formation. This process may be repeated a plurality of times along a length of the horizontal section to stimulate the plurality of zones of the subterranean formation.
Generally, the traditional stimulating processes fluidly isolate the portion of the casing conduit from downhole portions of the casing conduit, and corresponding regions of the subterranean formation that are in fluid communication therewith, using isolation plugs or using isolation balls and seats. Isolation plugs may include and/or be expandable plugs that may be located within the casing conduit and subsequently expanded to fill a portion of the casing conduit, thereby blocking fluid flow therepast. Isolation balls may include and/or be elastomeric balls that are sized to fit within the casing conduit and to seal with a respective seat that is sized to receive the isolation ball to block the flow of fluid therepast.
However, as the length of the well is increased, setting the required number of isolation plugs becomes increasingly difficult and/or expensive and may inhibit economic and/or efficient stimulating of the subterranean formation. Moreover, the isolation plugs must be removed from the casing conduit, typically by time-consuming and/or expensive processes that include drilling the isolation plugs from the casing conduit, prior to production of the reservoir fluid from the subterranean formation.
Similarly, isolation balls and seats rely on progressively smaller balls and seats to stimulate a desired number of zones of the subterranean formation. Thus, there is a practical limit to the number of zones that may be stimulated with isolation balls and seats while still permitting sufficient fluid flow rates within the casing conduit. In addition, the progressively smaller seats effectively may limit access to portions of the casing conduit that are downhole therefrom, as many downhole assemblies simply may be too large to fit, or flow, through the seats. Furthermore, these seats often must be removed from the casing conduit prior to production of the reservoir fluid from the subterranean formation, and doing so increases the overall cost of the stimulation process. Thus, there exists a need for improved systems and methods for stimulating a subterranean formation.